Perspective drafting system

ABSTRACT

A device for making one-, two- or three-point perspective drawings consisting of a rotatable drafting surface, a parallel straightedge and the rotating surface for conjoint movement.

United States Patent Barzee 5] Mar. 7, 1972 [54] PERSPECTIVE DRAFTING SYSTEM [56] Reterences Cited 72 Inventor: Verl N. Barzee, 70s Knickerbocker.Dr., UNUED STATES PATENTS Sunnyvale, Calif. 94087 2,478,751 8/1949 De Postels ..33/77 [22] Filed: May 20,1970 3,345,751 10/1967 Barzee eta].

[21] Appl.No.: 39,049 Primary Examiner-Harry N. Haroian Attomy-Milmore & Cypher [52] Us. (*1 W77 57 ABSTRACT g; .3431 A device for making one M} or mewoim perspective drawings consisting of a rotatable drafting surface, a parallel straightedge and the rotating surfacefor conjoint movement.

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SHEET 9 [IF 9 l/ERL M BARZEE INVENTOR ATTORIVEY$ PERSPECTIVE DRAF'IING SYSTEM BACKGROUND OF THE INVENTION Present devices for assisting in the preparation of perspective drawings only provide a fixed set of vanishing points. Obviously such devices are limited because of the need to draw views from various angles and with various vanishing points to clearly illustrate certain features.

Where more than one draftsman is assigned to a particular perspective drawing it is extremely difficult for the second draftsman to follow the work of the first draftsman.

At the present time, most. perspective drawings are not drawn to an accurate scale, which limits their usefulness except for very limited purposes.

SUMMARY OF THE INVENTION The gist of the invention is the discovery that by releasably linking a straightedge and a rotary table together, accurate one-, twoand three-point perspective drawings could be drawn.

An object of the present invention therefore is to provide a tool for draftsmen which they can use to prepare perspective drawings quickly, accurately and to scale.

Another object is to provide a drafting tool for making perspective drawings relatively inexpensive and can be used with present drafting tables.

A further object is to provide a device for making perspective drawings which will permit standards to be established where desired, in regard to vanishing points.

A still further object is to provide a drafting tool which will pennit three-point vanishing points tm be established from aerial photographs regardless of the angle from which the photographs were taken.

Still another object is to provide a device which will permit several lines to be drawn which relate to the same vanishing point without making any change in the setup of the device.

Yet another object is to provide a device which will permit the rotatable table to be locked in position so that all drawn lines along the same ray leading to a vanishing point may be drawn precisely in alignment permitting the drawing of several aligned parts with one setting of the straightedge.

A still further object is to provide a mechanism for drawing perspective drawings which is constructed from a few relatively simple rugged parts which can be operated without repair or need for adjustment by the average draftsman with relatively little instruction.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the device constructed in accordance with the present invention.

FIG. 2 is an enlarged side view of a portion of the device with some parts in cross section taken along the line 22 of FIG. 1.

FIG. 3 is an enlarged cross-sectional view of a portion of the device taken along the line 33 of FIG. 1.

FIG. 4A is an enlarged cross-sectional view of a portion of the device taken substantially along line 44 in FIG. 1.

FIG. 4B is an enlarged cross-sectional view taken along line 4B4B of FIG. 4A. I

FIG. 4C is a cross-sectional view of a portion of the device taken along line 4C-4C of FIG. 48.

FIG. 5 is an enlarged cross-sectional view of a portion of the device taken substantially along line 5-5 of FIG. 1.

FIG. 6 is an enlarged cross-sectional view of a portion of the device taken substantially along line 6-6 of FIG. 1.

FIG. 7 is an enlarged cross-sectional view of a portion of the device taken substantially along line 7-7 of FIG. 1.

FIG. 8 is an enlarged cross section of a portion of the device taken along the line 8-8 of FIG. 1.

FIG. 9 is an enlarged cross section of a portion of the device taken along line 9-9 in FIG. 1. 1

FIG. 10 is an enlarged cross-sectional view of a portion of the device taken along line 10l0 in FIG. 11.

FIG. 11 is a partial top view of a portion of the device withportions in cross section and some parts in phantom line for purposes of illustrating movement of some parts to show the operation of the device.

FIG. 12 is an enlarged plan view of a portion of the device taken substantially along line l2-l2 of FIG. 11 with portions removed and with some parts in phantom line to show different positions of particular parts.

FIG. 13 is an enlarged cross section of a portion of the device shown in FIG. 12 taken along line l3--13.

FIG. 14 is an illustration of the type of drawing that a person can easily make using the device of the present invention when two vanishing points are established.

FIG. 15 is an illustration ofanother type of drawing that can be made using the device of the present invention when two vanishing points are established on the horizon line.

FIG. 16 is another illustration of the type of drawing that can be made using the device of the present invention when three vanishing points are established.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention may be used with a drafting table having a rotatable circular drafting surface such as the type shown in my U.S. Pat. Nos. 3,345,751; 3,328,886 and 3,311,070 or it may be used with a conventional drafting table. When used with my patenteddrafting table, only minor modifications need be made to the straightedge, and but a single part, viz, the link means need be added.

Since most offices which anticipate using the present perspective drive mechanism have drafting tables which do not have a rotating drafting surface, this application describes in detail a specific apparatus which can be used with any ordinary drafting table.

DRAFTING SURFACE FIG. 1 shows a standard drafting table 1 which may be made of any material such as wood or metal or as shown in the drawings, the board could be made of modern materials such as a sandwich of hard foam sty rofoam or other type of foam 2 bonded to sheets of 0.020 aluminum 3 and 4. Generally such surfaces are covered by a sheet of vinyl 6. v

The frame 7 for carrying the rotatable drafting surface is described in my patents mentioned above or it may be con-' structed as shown in FIGS. 8 and 9 with a rigid sheet of material 11 such as plexiglas covered by a sheet of vinyl 12.

The rotatable frame may be mounted in several ways, some of which are shown in my patentsset forth above. Another form is shown in FIG. 8 wherein a recess 13 is formed in the board and a hub 14 having an annular vertical member 16 is inserted into the recess and an annular horizontally disposed flange l7 rests on the top surface of the board surrounding the recess. A ball bearing 18 carried by the .hub journals a vertical shaft 19 which is connected to the rotatable drafting surface. On the other end of the shaft is mounted a magnetic material 21. A pennanent magnet 22 is connected to the board in the recess and is spaced from the magnetic material so that it releasably holds the magnetic material but does not touch it so as to prevent rotation.

STRAIGHTEDGE This invention may be used with any straightedge with some modification as set forth below. An ideal straightedge arrangement, however, is described in my U.S. Pat. No. 3,328,886. The relevant features of that system are shown in FIGS. 1, 3, 4A, 5, 6, and 11 of the drawings. Briefly, the parallel straightedge 23 is carried by flexible members 24 and 26 which are threaded through sheave mountings 27 and 28 carried by the straightedge. The flexible members are connected to board mounting members 27, 28, 29, and 31. The advantages of the particular mountings shown are described in my U.S. Pat. No. 3,328,866 but the feature stressed here is the ability to adapt to any board and the adjustment of the elevaplished. This feature is shown in FIG. 3. An upright threaded member 32 is attached to an upright channel member 33. An internally threaded female member 34 with a thumbscrew 36 moves a downwardly turned channel member 37 against the bias of spring 38. An L-shaped member 39 carries the mounting member carrying the flexible member. In operation the straightedge may be moved closer to the drafting surface by screwing the thumbscrew down against the biasing force of the spring. Loosening the screw permits the spring to raise the entire assembly.

The straightedge mounts may be attached to the board in various ways but one method is shown in FIG. 6, in which a shaped member 41 serves to attach to the edge of the board and to bottom mounts. An upright portion 42 serves as a pencil tray. The channel members 37 and 42 upon which the mounting members are attached run the length of the board as shown in FIG. 1. Adjustments can be made at each comer by the other thumbscrews 43, 44, and 46.

LINK MEANS The heart of the invention is the link means 47 which is mounted on the straightedge for longitudinal reciprocating movement and releasably connected to the planar surface of the rotating frame for conjoint movement. It is here that the widest variation in design may occur but the fundamental principle of the link means is to cause a predetermined rotation of the drafting surface for a predetermined movement of the straightedge. Further, the point of attachment of the link to the drafting surface represents the vanishing point selected, and this point should be on the leading edge 48 of the straightedge or as near to it as possible. The drafting surface should pivot about the point of attachment and of course the link must slide transversely upon rotation of the drafting surface.

The link means is here shown as a T-shaped member having spaced sleeve bearings 49 and 51 which ride an elongated bar 52 running substantially the length of the straightedge. In its simplest form, a suction cup 53 is rotatably attached to the link. Since the attachment must be made and broken repeatedly, a cup with an annular raised flange 54 is useful in providing a way to break the seal with a finger.

The suction cup does tend to creep and because of the difficulty in reattaching the cup at the same point, it is helpful to provide a registration pin 56 on the axis of rotation of the cup which should be coincident with the selected vanishing point.

The assembly for mounting the registration pin consists of bearings 54 in a cylindrical cavity in the head section of the T- shaped member which journal an internally threaded screw 58. A hollow externally threaded screw 59 is threadably mounted in the opposite end and has an opening through which the pin passes. The pin has an enlarged head portion 61 and is biased downwardly by a spring retained by plug 63.

The registration pin registers with various types of releasable pin means such as magnets or cavities in the board or temporary or permanent attachments to the board. As shown in FIGS. 48 and 4C, a suitable registration means may be constructed with a disc 64 having a cavity 66 for receiving the end of the pin. A sheet of vinyl 67 of about 0.040 to 0.060 inches cemented to the disc provides an excellent means of attachment to the vinyl sheet covering most drafting boards. With the vinyl to vinyl attachment, one to three of the discs can be spotted at the selected vanishing points and left until the drawing is completed. Because of their thinness, the

straightedge will ride over them without contact.

SLIDE BAR The slide bar is preferably constructed as a part of the straightedge, but again, since this application is primarily directed to the perspective drafting system as an attachment to existing equipment, one type of adapter is shown in the drawings in FIGS. 1, 4A and 11. Two channelshaped members 68 and 69 are attached at either end of the straightedge by setscrews 71 which clamp to either side of the trapezoidal shape member 72 provided as a handhold on most straightedges. The slide bar 52 is received in openings in the sides of the channel-shaped members. Preferably the slide bar is of circular cross section to permit pivoting of the link means and constructed of steel to provide a smooth long-wearing slide.

SELECTION BRAKE MEANS A selection brake system for my drafting table apparatus is fully described in my US. PatJNo. 3,345,751. A completely new selection brake apparatus was necessary however, for use with the present perspective drawing system whichcan be purchased as a unit for any drafting board. The problem presented by such criteria is fully exemplified in FIG. 9 in which as may be seen, the entire mechanism must fit between the top of the drawing board and the top surface of the rotatable drafting surface.

Briefly, the selection brake means consists of a base 73; a spring detent 74 mounted on the base; an elongated arm 76 pivotally mounted at point 77 on the base for selective movement between a first indexing position indicated by arrow 78; a second freewheeling position indicated by arrow 79 and a third infinite braking position indicated by arrow 81. The arm has an end 82 releasably engageable in the second position; a cam surface 83 releasably engageable with indexing means in the first position; and a brakeshoe 84 mounted on the distal end 86 of the arm for frictional engagement with the rotatable frame. Within the arm a longitudinal slot 87 is fonned. A manually engageable bellcrank 88 is pivotally mounted at point 89 on the base and has an end 91 slidably engageable in the longitudinal slot by means of a sleeve 92. A spring 93 is connected to the base and the bellcrank in an overcenter position so as to releasably hold the arm in the first and third positions.

The brakeshoe preferably has a rubber surface 94 as shown in FIG. 13 which contacts the edge 96.0f the rotatable drafting surface.

INDEXING MEANS AND PERIPHERAL SUPPORTS An indexing means is fully described in my US. Pat. No. 3,345,751 and the system here shown and described is suitable for systems for use with standard drafting boards.

The peripheral supports are best shown in FIG. 9 and consist of a small roller wheel 93 mounted on an axle-94 connected to a bracket 96 which is connected to the frame carrying the rotatable drafting surface by a countersunk screw 97.

The indexing means consists of circular plastic stubs 98 which are connected to the rotatable frame with the same screw that connects the roller wheels. The indexing means are spaced around the periphery of the drafting surface at predetermined angles. For purposes of exact angular peripheral spacing, the screw is placed in the circular stub at an eccentric opening 99 so that final adjustment may be made by turning the stub as seen in FIG. 3.

The indexing means is operated by several difierent types of mechanisms. In FIG. 1, a control arm 101 is connected to the bellcrank. An alternative device is shown in FIGS. 10 and 11 where a control arm 102 is connected to the bellcrank and the other end of the arm is connected to a thumb wheel 103. The thumb wheel is joumaled for rotation on a bolt 104 connected to the board by locknut 106. A spacer 107 spaces the wheel from the board. The control arm is formed with a slot 108 in which a stub shaft 109 connected to the thumb wheel depends.

VERNIER Very precise angular displacements can be obtained by marking the periphery of the drafting surface at each degree or multiple degrees. A vernier 111 with vernier lines 112 is mounted as shown in FIG. 1.

OPERATION Examples of the type of work that can be done by the present invention are shown in FIGS. 14, 15, and 16.

In FIG. 14, various articles 113 and 114 for example are drawn on a sheet of drawing paper 116. The first vanishing point 117 is established by placing the registration means shown in FIG. 4 directly over the vanishing point. Each line leading to vanishing point 117 such as lines 118, 119, and 121 are drawn by the straightedge and without the use of triangles or protractors. As the straightedge is moved, the drawing is automatically rotated to the correct position. The second vanishing point occurs off the page of FIG. 14 but ray lines 122 are shown leading to it.

FIG. shows a building 123 drawn by the instant device using two vanishing points 124 and 126 located on a horizon line 127 with the center of the drafting surface or axis of rotation at point 128. Note the manner in which all horizontal lines lead to the two vanishing points and all of the vertical lines are in true vertical.

FIG. 16 is an unusually good illustration of the manner in which the present invention may be used. In this drawing, three vanishing points are used. All of the vanishing points are located off the drawing but rays 129 lead to a first vanishing point; rays 131 lead to a second vanishing point and rays 132 lead to third vanishing point. The center of the drawing surface and the axis of rotation is located at point 133.

Iclaim:

l. A perspective drafting device comprising:

a. a frame carrying a planar drafting surface mounted for axial rotation;

b. a straightedge mounted for parallel reciprocating movement over said surface; and

0. link means mounted on said straightedge for longitudinal reciprocating movement and being releasably connected to said planar surface for conjoint movement therewith.

2. A drafting device as defined in claim 1 comprising:

a. said link means having a suction cup mounted thereon for releasable attachment with said drafting surface.

3. A drafting device as defined in claim 2 comprising:

a. said link means including a registration pin substantially coincident with the selected vanishing point; and

b. means mounted on said drafting surface for releasably engaging said pin.

4. A drafting device as defined in claim 2 comprising:

a. said suction cup being mounted for rotation about an axis parallel to the axis of rotation of said drafting surface.

5. A drafting device as defined in claim 4 comprising:

a. a slide bar mounted on and parallel to the edge of said straightedge; and

b. bearing means mounted on said link means permitting free sliding movement of said link along said slide bar.

6. A drafting device as defined in claim 1 comprising:

a. means for selectively restraining turning of said rotatable drafting surface.

7. A drafting device as defined in claim 6 for use on a drafting table comprising:

a. means supporting the periphery of said rotating surface above the surface of said drafting table, and

b. means suspending said straightedge above said drafting table and said planar drafting surface.

8. A drafting device as defined in claim 7 comprising:

a. said means supporting the periphery including a plurality of rollers;

b. indexing means carried by said rotating drafting surface;

and

c. means for selectively engaging said indexing means.

9. A drafting device as defined in claim 8 comprising: a. said selection means having:

1. a base, 2. a spring detent mounted on said base,

3. an elongated arm pivotally mounted on said base for selective movement between a first indexing position, a second freewheeling position and a third infinite braking position, said arm having an end releasably engageable in said second position, a cam surface releasably engageable with said indexing means in said first position, and a brakeshoe mounted on the distal end of said arm for frictional engagement with said rotatable frame and a longitudinal slot formed therein,

4. a manually engageable bellcrank pivotally mounted on said base and having an end slidably engageable in said longitudinal slot,

5. spring means connected to said base and said bellcrank in an overcenter position so as to releasably hold said arm in said first and third positions, and

b. said selection means being mounted on the surface of said drafting table and having a height permitting unrestricted passage of said straightedge over said means.

10. A drafting device as described in claim 9 comprising:

a. a thumb wheel rotatably mounted on the surface of said drafting table remote from said selection means, and

b. link means connecting said thumb wheel and said bellv crank for movement of said selection means arm to said first, second and third positions by mere rotation of said thumb wheel.

11. A device as described in claim 1 comprising:

a. a drafting board;

b. a permanent magnet recessed in said drafting board;

c. a hub adapted for removable registration with said recess;

d.- a shaft mounted for rotation in said hub and adapted for connection to said frame carrying said drafting surface; and

e. a magnetizable material carried by said shaft in spaced relation to said magnet permitting rotation of said shaft and releasably holding said rotatable frame to said drafting board. 

1. A perspective drafting device comprising: a. a frame carrying a planar drafting surface mounted for axial rotation; b. a straightedge mounted for parallel reciprocating movement over said surface; and c. link means mounted on said straightedge for longitudinal reciprocating movement and being releasably connected to said planar surface for conjoint movement therewith.
 2. A drafting device as defined in claim 1 comprising: a. said link means having a suction cup mounted thereon for releasable attachment with said drafting surface.
 2. a spring detent mounted on said base,
 3. an elongated arm pivotally mounted on said base for selective movement between a first indexing position, a second freewheeling position and a third infinite braking position, said arm having an end releasably engageable in said second position, a cam surface releasably engageable with said indexing means in said first position, and a brakeshoe mounted on the distal end of said arm for frictional engagement with said rotatable frame and a longitudinal slot formed therein,
 3. A drafting device as defined in claim 2 comprising: a. said link means including a registration pin substantially coincident with the selected vanishing point; and b. means mounted on said drafting surface for releasably engaging said pin.
 4. A drafting device as defined in claim 2 comprising: a. said suction cup being mounted for rotation about an axis parallel to the axis of rotation of said drafting surface.
 4. a manually engageable bellcrank pivotally mounted on said base and having an end slidably engageable in said longitudinal slot,
 5. spring means connected to said base and said bellcrank in an overcenter position so as to releasably hold said arm in said first and third positions, and b. said selection means being mounted on the surface of said drafting table and having a height permitting unrestricted passage of said straightedge over said means.
 5. A drafting device as defined in claim 4 comprising: a. a slide bar mounted on and parallel to the edge of said straightedge; and b. bearing means mounted on said link means permitting free sliding movement of said link along said slide bar.
 6. A drafting device as defined in claim 1 comprising: a. means for selectively restraining turning of said rotatable drafting surface.
 7. A drafting device as defined in claim 6 for use on a drafting table comprising: a. means supporting the periphery of said rotating surface above the surface of said drafting table, and b. means suspending said straightedge above said drafting table and said planar drafting surface.
 8. A drafting device as defined in claim 7 comprising: a. said means supporting the periphery including a plurality of rollers; b. indexing means carried by said rotating drafting surface; and c. means for selectively engaging said indexing means.
 9. A drafting device as defined in claim 8 comprising: a. said selection means having:
 10. A drafting device as described in claim 9 comprising: a. a thumb wheel rotatably mounted on the surface of said drafting table remote from said selection means, and b. link means connecting said thumb wheel and said bellcrank for movement of said selection means arm to said first, second and third positions by mere rotation of said thumb wheel.
 11. A device as described in claim 1 comprising: a. a drafting board; b. a permanent magnet recessed in said drafting board; c. a hub adapted for removable registration with said recess; d. a shaft mounted for rotation in said hub and adapted for connection to said frame carrying said drafting surface; and e. a magnetizable material carried by said shaft in spaced relation to said magnet permitting rotation of said shaft and releasably holding said rotatable frame to said drafting board. 